The present invention relates to an apparatus for correcting and diagnosing angular rate sensors installed in an automotive vehicle which is capable of judging whether or not the angular rate sensors are generating correct output signals.
When diagnosis or correction for the offset of angular rate sensors is performed in respective angular rate sensors, an automotive vehicle system sends a vehicle speed signal to respective angular rate sensors. Based on this vehicle speed signal, it is checked whether or not the automotive vehicle is stationary or stopped before diagnosing or correcting the offset in outputs of respective angular rate sensors.
Hereinafter, as one example of such an apparatus performing the offset correction for angular rate sensors, the inertia sensors installed in an automotive vehicle will be explained with the attached drawing. FIG. 7 is a block diagram showing an inertia sensor installed in an automotive vehicle and an associated signal processing section.
As shown in FIG. 7, an automotive inertia sensor J1 consists of two acceleration sensors J2 and J3 and a single angular rate sensor J4. The acceleration sensor J2 detects an acceleration of an automotive vehicle in the lateral (right and left) direction, and the acceleration sensor J3 detects an acceleration of this automotive vehicle in longitudinal (back and forth) direction. The angular rate sensor J4 detects an angular rate of the automotive vehicle. Furthermore, a wheel speed sensor J5 detects the rotational speed of a wheel of the automotive vehicle. An electronic control unit (hereinafter, referred to as ECU) J6 receives detection signals of these sensors J2 to J5 and processes the received signals. In this respect, ECU J6 acts as a signal processing section for the automotive inertia sensor.
ECU J6 includes a vehicle stopped condition judging section J7, an offset diagnosing section J8, and a control section 19. The vehicle stopped condition judging section J7 judges whether a wheel is rotating or not based on the detection signal obtained from the wheel speed sensor J5. In other words, the vehicle stopped condition judging section J7 judges whether or not the automotive vehicle is stopped or stationary. The vehicle stopped condition judging section J7 outputs a signal indicating a stopped condition of the automotive vehicle according to its judgment result.
The offset diagnosing section J8 receives the detection value of angular rate sensor J4 and the signal indicating a stopped condition of the automotive vehicle sent from the vehicle stopped condition judging section J7. The offset diagnosing section J8 obtains an offset of the angular rate sensor J4 based on a detection value sent from the angular rate sensor J4 in a condition that the automotive vehicle is stopped. More specifically, the detection value of angular rate sensor J4 should be zero when the automotive vehicle is in a stopped condition. If the detection value of angular rate sensor J4 is not zero, there will be a significant offset corresponding to the detected value. This offset value is compared with a predetermined value to perform an offset diagnosis. When the offset value is smaller than the predetermined value, the detection value of angular rate sensor J4 is subtracted by the offset amount. The obtained value is used as a new angular rate value reflecting a corrected offset.
The control section J9 is an ECU which is, for example, equipped in a brake control system or in a navigation system. The control section J9 executes various calculations based on entered signals for obtaining automotive vehicle driving conditions used, for example, in the brake control or in the automotive vehicle navigation.
However, in a situation that no vehicle speed signal is obtainable from the automotive vehicle system, the above-described diagnosis will be unfeasible. Considering this drawback, for example as disclosed in the Japanese Patent No. 3404905, it is possible to judge whether the automotive vehicle is stopped or not based on the signals of acceleration sensors J2 and J3 which can detect vibrations of the automotive vehicle in a driving condition.
However, according to the above-described prior art document, it is impossible to judge whether or not an output signal of the angular rate sensor J4 represents a true angular rate in a condition that the angular rate sensor J4 outputs this value in a turning condition of the automotive vehicle. Accordingly, it is impossible to diagnose the sensitivity of angular rate sensor J4. Furthermore, according to a method using a signal obtained from the wheel speed sensor J5, it is impossible to correct the offset of angular rate sensor J4 due to the arrangement of inertia sensor J1.